In materials handling vehicles such as fork lift trucks, it is desirable to vary the amount of braking force applied so that the vehicle may be gradually slowed and yet have a high static torque for parking the vehicle on inclines. Hydraulic brakes provide for great flexibility in the amount of braking force applied, but hydraulic brake systems are expensive because of the required space for hardware and plumbing. Electric brakes are frequently used in materials handling vehicles, particularly electrically powered vehicles, because of their size and simplicity. However, electric brakes normally do not lend themselves to being variable in the braking force applied, and they require separate parking and dynamic braking assemblies.
In another application, workers are routinely elevated above the body of the vehicle in a carriage. When a worker is in this position and the vehicle is in motion, it is also desirable to apply braking force gradually to minimize the amount of vibration experienced by the worker who is elevated in the carriage. Here again electric brakes are frequently used, but they can be marginally effective in these gradual braking force applications. An electric braking system which varies its braking force to gradually stop a vehicle without sliding the wheels and yet provide high static torque for parking the vehicle on inclines and the like is needed.